I just finished listening to an interesting podcast featuring Dr. Zeisel, a researcher at the NC Nutrition Research Institute. The interview discussed the body’s need for choline and the impact of some genetic variants on our ability to produce it in the body. So I decided to dig into this a little more and look at some of the SNPs covered by 23andMe data related to choline.
A little background information…
Choline is involved in several critical roles in the body including:
- supporting methylation reactions through donating a methyl group (TMG/betaine)
- formation of acetylcholine, a neurotransmitter and cell-signaling molecule
- formation of phosphatidylcholine which makes up cell membranes[ref]
- muscle function [ref]
- deficiency in choline contributes to non-alcoholic fatty liver disease
Recent studies of choline levels show:
- academic achievement in 15-year olds is significantly associated with plasma choline levels [ref]
- choline plus B-vitamins may increase neuroplasticity and speed recovery after a stroke [ref]
- crocodile choline may be a treatment of gastric cancer [ref]
- choline deficiency is correlated to lower bone mineral density [ref]
- high serum choline concentrations may increase the risk of colon cancer [ref]
Generally, people can make some choline in their liver; a percentage of people have genetic variants that reduce their ability to make choline and need to ensure adequate intake through food or supplements.
Choline is the precursor to acetylcholine, which is a neurotransmitter. Acetylcholine controls muscles, heart rhythm, and other function.
The FDA gives a recommended adequate intake for adults as 425-550 mg/day. [ref]
Genetic Variants Related to Choline
PEMT – phosphatidylethanolamine N-methyltransferase
The PEMT pathway is responsible for the body’s production of phosphatidylcholine which is part of the phospholipid bilayer making up the membranes surrounding our cells. Note that 23andMe does not cover all of the SNPs in PEMT that are relevant to choline levels.
CHKA – Choline kinase alpha
The first step of the CDP-PC pathway.
rs10791957: (v.4 and v.5) A/A and A/C variants have a lower turnover of methionine to PC
“Specifically, the variant appears to decrease the use of dietary choline for PEMT-PC synthesis relative to CDP-PC synthesis. Variant individuals displayed decreased turnover of choline-derived methionine → PEMT-PC over the study period, indicating decreased activity of PEMT relative to women without the variant, and also tended to exhibit lower relative PEMT-PC/CDP-PC enrichment as compared to non-variants.”[ref]
In another study, those with C/C were found to be “less likely to have clinical symptoms after consuming a low-choline diet.” [ref]
BHMT – Betaine-homocysteine S-methyltransferase
rs3733890: (v.4 and v.5) A/A and GA variants have lower conversion of choline to betaine and more conversion of choline to CDP-PC
“Together, these results indicate that the variant favors the use of dietary choline for CDP-PC synthesis at the expense of betaine synthesis.” [ref]
FMO3 – Flavin-containing monooxygenase
rs2266782: (v.4 and v.5) GA and A/A variants have greater turnover of betaine to methionine and greater turnover of choline-derived methionine to PEMT-PC
“While a previous study from our group suggested that the variant might be associated with increased use of choline as a methyl donor in men (based on increased DMG pool size) , results from the present study, indicate that women with the variant actually use choline less as methyl donor. Variant women tended to have a lower turnover of betaine → methionine over the study period. In addition, variant women exhibited a greater turnover of choline-derived methionine → PEMT-PC over the study period, which is consistent with previous findings from our lab that have identified lower methionine excretion among variant individuals (i.e., a greater use of methionine may reduce excretion)” [ref]
MTHFD1 – methylenetetrahydrofolate dehydrogenase, cyclohydrolase and formyltetrahydrofolate synthetase 1
rs2236225 (G1958A): (v.4 and v.5) Carriers of the A allele are more likely to have choline deficiency on a low choline diet (modified by folate intake) [ref] [ref] In one study with premenopausal women, those with an A-allele were 15 times more likely to show choline deficiency symptoms on a diet low in choline.
Food and supplements:
Excellent (egg-cellent :-) sources of choline in foods include: eggs, liver, shitake mushrooms, milk, and various meats. [ref] Raw egg yolks are a better source of choline than cooked, but there are drawbacks, especially if you don’t know the source of your eggs.
More to read:
Dr. Amy Yasko also has a lot of information about the role of choline in the methylation cycle. Her view is that MTHFR variants can be bypassed using choline if a person doesn’t have BHMT or PEMT variants. Her free book Companion Guide: Feel Good Nutrigenomics is a good place to start, and her full book Feel Good Nutrigenomics as well as videos, etc can be found on her website.